WEB LISTING B: Trigger That Identifies Which Columns Were Updated

CREATE TRIGGER trg_T1_u_identify_updated_columns
  ON T1 FOR UPDATE
AS
SET NOCOUNT ON

DECLARE @i AS int, @num_cols AS int
DECLARE @UpdCols TABLE(ordinal_position int NOT NULL PRIMARY KEY)

SET @num_cols =
 (SELECT COUNT(*)
  FROM INFORMATION_SCHEMA.COLUMNS
  WHERE TABLE_SCHEMA = 'dbo'
    AND TABLE_NAME = 'T1')

SET @i = 1
WHILE @i <= @num_cols
BEGIN

  IF (SUBSTRING(COLUMNS_UPDATED(),(@i - 1) / 8 + 1, 1))
       & POWER(2, (@i - 1) % 8) = POWER(2, (@i - 1) % 8)
    INSERT INTO @UpdCols VALUES(@i)

  SET @i = @i + 1

END

SELECT COLUMN_NAME AS updated_column
FROM INFORMATION_SCHEMA.COLUMNS AS C JOIN @UpdCols AS U
  ON C.ORDINAL_POSITION = U.ordinal_position
WHERE TABLE_SCHEMA = 'dbo'
  AND TABLE_NAME = 'T1'
ORDER BY C.ORDINAL_POSITION
GO